1. Field of the Invention
This invention is in the general field of determining the relationship of earth handling machines, such as bulldozers and the like, to their location relative to grade, and to surrounding reference points.
2. Description of the Prior Art
Various prior art devices have been developed to determine the angle of earth moving machines.
U.S. Pats. Nos. 2,189,699 (Blunk), 2,333,988 (Demond), 2,412,831 (Owens), 2,467,157 (Schiavi), 2,486,697 (White), 2,565,615 (McCoy), and 3,564,531 (Burgin) show pendulums or other angle sensing mechanisms with pointers directly attached. These pointers point to markings on dials which indicate pendulum angle. The pointers move the same number of degrees as their corresponding pendulums. A difficulty found with this arrangement is that precise angle readings require long pointers and large dials.
U.S. Pat. No. 4,511,005 (Brown) shows a pendulum which drives a pointer via a pair of gears. The gear teeth are exposed to open air, and thus are vulnerable to dust contamination. Dust contamination is a major consideration, since earth moving machinery often operates in dusty environments. Furthermore, the Brown apparatus is large in overall height.
U.S. Pat. No. 2,412,831 (Owens) shows another angle measuring device with gearing to enable precise angle settings. The gears of this device are also exposed to air. Furthermore, these gears and their appended wheels only partially overlap each other, taking up more space than would fully overlapping wheels of the same size.
Devices of the prior art have generally been found to suffer from one or more of the following drawbacks: large bulk and/or weight, high manufacturing cost, inconvenient operation, and inaccuracy.